Time delayed switch



July 30, 1957 L. J. REYNOLDS TIME DELAYED SWITCH Filed Oct. 8, 1953 9/? o M; INVENTOR.

ATTORNEYS 2,801,313 TIME DELAYED'SWITCH Le wis 1. Reynolds, Houston, Tex., 'assignor, by'mesne as- 'lhisinvention relates 'to a time delayed .switch, and more particularly to. an improved electric curent flow "cutoff'device which, when-located in ancletric circuit,

enables the circuit to remain closed for a limited time interyal following switch actuation to a circuit opening position.

object of the invention is to provide a simplified structure which will be economical to manufacture and reliable in operation and which in use will maintain a closed circuitin current flowrelation for a predetermined time after a circuit opening manipulation'has been'made. 'By way of example, a household installation wouldhave a wall switch in a room lighting circuit, and when the 'roomds' tob'e darkened the-switch-is moved to an off position but the light will continue room illumination for a few minutes, during which a per-son could'leave the li g'hte'd'room or could see his-wayto lie down in bed and possibly be asleep before the room is in darkness. Various tir'nesettings and uses canbe employed.

A further object of the invention is to provide a delayed action cutoff making use of a thermally expansible liquid whose volume is controlled to make and thereafter break -a circuit through the-application and-removal of heat to the' liquid, with the openingof the circuit occurring upon temperature and volume reduction.

More specifically the invention deals with a circuit con taining a heater to raise the temperature of a column of mercury or similar fluid and thereby expand the same to maintain a pair of contacts closed, there being an arrangement operable at will to render the heater ineffective, whereupon the temperature of the mercury returns to normal,'with a resultant volume contraction to open the currentflow path between the contacts after a predetermined delay dependent upon the cooling olf period.

The'invention will be better understood upon'reference to the accompanying drawing, wherein Figs. 1 and 2 are circuit diagrams illustrating mercury switch'embodimentsin one of which the switch and heater are in parallel circuit and'in the other of which the switch and heater are in series circuit.

Referring first to Fig. 1, themercury switch is illustrated as including a closed container or capsule 1 having opposite enlargements or bulbs 2 and 3 connected by a narrow central neck portion of small diameter 'to contain a body of mercury or other fluid 4 which whenatnormal temperature is contained primarily in the lower bulb Z at a low level within the central neck portion. When heat is applied to the mercury, the column will rise beyond the narrow neck and into the expansion space provided by the uppermost bulb 3. For convenience the mercury container 1 may be formed of glass, and it has projected through and fused and sealed in opposite end walls a pair of contacts or electrodes 5 and 6 which end in spaced apart relation to one another so as to be bridged by the current conducting mercury when expanded. When the mercury bridge has given up its heat, its level will fall to re-establish the gap between the spaced electrodes or contacts 5 and 6. As shown in Fig. 1, the

United State ice lower contact is fully submerged in the liquid at all times,

and theupper c'ontact6 is submerged only when the liquid 'l'evelrises above the lower height of the contact. This arrangement can be'variously modified; as, forexample, thetwo electrodes may be arranged side by side or projected laterally into the container with both terminating entirely above the contracted liquid level.

Anelectrically energized heater element or resistance wire 7 is located in close proximity with the body of mer- :when current is flowing therethrough.

Suitable conductor wires-join the heater 7 and the mercury switch in parallel relation to one another, and each in series with 'a current responsive indicator as a light bu1b 8'. Other types of electrically energized units may be used in place of thelight bulb 8 if the switch is to be employed for other than controlling a lighting circuit. Giircuits through boththe heater and the mercury switch are controlled as by means of a multiple way switch and the usual conductor wires, and a simplified illustration of the multiple switch includes a pivotal means as a swingable'bl-ade 9 for selective movement between several positions. 'In "the full line position shown, the blade 9 engages a contact 10 whose conductor leads to the elec: trodes, and this may be referred to as the delayed off position. -In'the broken line position of the blade, indicating that the blade has been swung to the right, in Fig. -1, a'contacv 11 will receive current for flow to the heater 7, and this-"position may bereferred to as the on position; An optional instantaneous off position of the blade is indicated by dotted lines with the blade swung toward the left in Fig. 1.

In the full line relation of the parts shown, no current is supplied to the light bulb 8. As soon as the blade 9 is swung into engagement with the contact 11, the lamp will be instantaneously lighted and current flowing through the heater 7 will raise the temperature of the mercury body 4 and raise its level for submerging both the'electrodes 5 and '6. Thereafter, if the switch blade 9 is swung to the instantaneous off position, the supply of current is immediately cut off and the light bulb 8 is extinguished. 0n the other hand, if the switch blade 9 is returned for engagement with the contact 10, current flow through the heater is cut off but current flow then continues through the expansible body and the electrodes Sand 6 for continuously supplying cur-rent for constant illumination 'of the lamp 8 so long as the temperature of the fluid body '4 keeps the volume at a level at which the electrodes are bridged. When the temperature finally drops to sufiiciently contract the liquid and thereby break the. pathof current flow between the electrodes, the lamp 8 will be extinguished.

In the embodiment shownin Fig. 2, current responsive indicator as the lamp 12 is inseries with a heater 13 and with spaced apart electrodes or contacts 14 and 15 mounted at the top and the bottom, respectively, of a mercury containing capsule 16. The capsule itself is pivoted at its lower end on a pin 17, and the mercury contained therein when cooled has a contracted volume to bring its level slightly below the position of the contact 14 when the container 16 is in an erect or vertical position, indicated by full lines in Fig. 2. In this relation the electric circuit is open, and when it is desired to close the circuit the container 16 is tilted to one side so that the mercury level rises above or is in contact with the contact 14 to provide a path of current flow between the contacts 14 and 15 and through the heater 13 and lamp 12. The heater is positioned closely adjacent the container when the container is tilted to its limit of full-on position, and supplies heat for a temperature and volume increase of the mercury so that when the con-" erect full line position is sufiicient to remdvstheeqntainer from the influence or field of heatfapplication. Any number of intermediateposit'ions of the container may be provided, and two intermediate positions are indicated by broken lines, both of which position .,th e

container at distances from the heaterwhich enablethe heater to be at least partially effective and to ane gtent which retards the rate of liquid coolingYotrI. Inkthis fashion the contraction of the liquid at diiferent rates affords a selection of time delay interval for the cutout of current flow. By proper'selectionof the volume of mercury and the location of the electrode 14 an instantaneous cutoff of current flow can be had in the vertical full line position of the container 16 if the hot volume places the liquid level just below the contact 14.

c For holding the pivoted container 16 in any of its desired positions of adjustment, a bar 18 has one end pivotally mounted at 19 with its intermediate portion extending along an arc defined by the free swinging end of the container 16 so as to engage the same This arcuate portion of the bar 18 is provided with a series of retainingnotches any one of which can receive the free end of the container and locate it in any position of adjustment. At its free end the link 18 is joined toone end of a tension spring 20 whose opposite endis suitably anchored in fixed relation with the pivot 17. This spring force alfords a yielding resistance to displacement of the link 18 aboutits pivot for insuring retention of the switch container in any position torwhich vit may be adjusted. 1

The invention as specifically described is subject to various modifications, such as come within the scope of the appended claims.

What is claimed is:

1. In a time delay electric switch for an electric circuit including a current responsive indicator, a container for thermally expansible liquid, means mounting said container for movement between on and off positions of said switch, a pair of electrodes carried by the container and projected into the container on position, an electric heater in series with the electrodes and positioned adjacent the on container position for the application of heat to said liquid to increase the volume thereof, the volume of liquid in relation to the electrodes being such that when the container is in its 011 position the path through-the liquid to the electrodes is closed by hot liquid and is open after the temperature of the liquid returns to normal, said switch including a conductor connecting said heater in series with said indicator.

2. In a time delay electric switch for an electric circuit having a current responsive indicator therein, a container movable between on and 011 positions, a pair of spaced electrodes extending within the container, a body of thermally expansible liquid confined within the container and of a hot volume which closes the space between the electrodes for current flow and a cold volume which breaks the current flow path when the container is in "01f position but maintains the current'flow path with the container in on position, and an electrical heater in series with said flow path and located adjacent the container on position for applying heat to the liquid and spaced from the container oft position to enable a liquid temperature drop, said switch including a conductor connecting said heater in series with said indicator.

3. In a delayed action switch for an electric circuit having a current responsive indicator therein, a heater, a container pivotally mounted for movement between an off position and an on position adjacent the heater for increasing container temperature, a pair of electrodes mounted in spaced apart relation within the container, and a body of thermally expansible liquid confined by the container and having a hot volume to close the space between the electrodes for completing a path of current flow between the electrodes and a cold volume which breaks said current flow path, said switch including a conductor connecting said heater in series with said indicator. 4 c 4. In a delayed action switch for an electric circuit having a current responsive indicator therein, a container enclosing a pair of spaced electrodes and a body of thermally expansible liquid, means pivotally mounting the container for movement between relatively upright and tilted positionsrelated to the volume of liquid so that the liquid level submerges both electrodes in the container tilted position and breaks the current flow path between the electrodes in the upright position with the liquid at normal temperature but closes the current flow path with the liquid at an elevated temperature, and an electric heater in series circuit with the electrodes and positioned adjacent the container tilted position for elevating liquid temperature, said switch including a conductor connecting said heater in series with said indicator.

5.1The structure of claim 4 wherein the position of the container is variable between said relatively tilted and upright positions to modify the intensity of heat application from the heater in controlling the rate of temperature drop and thereby the interval of cutoff delay following container movement away from fully tilted position.

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